In a common locking device, such as an exposed shackle type padlock (hereinafter referred to as a ‘padlock’), a U-shaped hinged shackle is passed through one or more rings (or through-holes), and the free end of the shackle inserted and retained in a bore on the housing of the padlock. The rings are now said to be locked using the padlock. An operator key is used to operate (lock and unlock) the locking device. The exposed shackle type padlock includes a central cylinder which turns an attached cam. This cam engages with a groove on the shackle, locking the padlock. Such a padlock also contains a set of locking pins that prevent a wrong key from operating the padlock. When the cylinder is rotated one way using an operator key, the cam moves to disengage the shackle, allowing the shackle to be lifted and rotated, thereby unlocking the exposed shackle type padlock. Since a unique operator key controls the operation of the exposed shackle type padlock, losing or misplacing the operator key will typically involve replacement of the padlock.
To save time and money associated with the replacement of the padlock, when the operator key is lost, an interchangeable core is commonly used with padlocks. The interchangeable core, first invented by Frank Best in 1912, has become the most commonly available type of interchangeable core cylinder, and is easily recognizable by the ‘figure-8’ shape of the core's face. This type of interchangeable core is now standardized and is offered by many commercial lock manufacturers. Competition in the market place has decreased the cost and increased the availability of these interchangeable cores, making them well suited for use with common locks. Since the interchangeable core contains the locking pins of the padlocks, the combination of the interchangeable core and an operator key controls the operation of these padlocks. In such exposed shackle type padlocks with an interchangeable core, a control key is used to remove the interchangeable core (with one combination) from the lock and replace it with a core having a different combination. A retaining tab that protrudes from the cylindrical surface of the interchangeable core engages with a cavity on the mating surface of the lock housing, locking the interchangeable core in the housing. With the interchangeable core locked in place in the housing, the operator key is used to control the operation of the padlock. This interchangeable core feature allows a locksmith to re-key a padlock in a matter of hours instead of a matter of weeks, if the operator key is misplaced.
In the padlock described earlier, the shackle is exposed, and therefore prone to attack (applying torque to the shackle, applying a tension force to the shackle, cutting the shackle, etc.). A hidden shackle style locking device (hereinafter referred to as a ‘hockey puck lock’) is sometimes used to prevent access to the shackle and thereby reduce such attack. A hockey puck lock has a generally stubby cylindrical shape with a rounded front and back surface. The rounded back surface defines a generally rectangular cavity to receive one or more parallel plates (which are to be locked together) with mating through-holes. A cylindrical shackle attached to a central cylinder having a locking mechanism is slidably disposed on the stubby cylindrical housing a retaining screw. The retaining screw permits the central cylinder and the shackle to freely slide in the housing, while preventing it from being detached from the housing. The shackle slides in the direction of its longitudinal axis, out of one wall of the rectangular cavity into a blind cylindrical cavity formed on the opposite wall of the rectangular cavity. To lock the parallel plates together within the rectangular cavity, the shackle passes through the mating through-holes of the parallel plates, while sliding from one wall of the rectangular cavity into the cylindrical cavity. When an operator key is inserted into the central cylinder and turned, notches on the side of the operator key operate a set of locking pins (as described earlier) on the central cylinder, and allow the central cylinder and the shackle to turn. When the shackle turns, a groove or a tab formed on the tip of the shackle engages with a corresponding geometry within the cylindrical cavity, thereby the locking the shackle in place.
While the typical hockey puck lock decreases the susceptibility of the locking device to attack, replacing the core involves a complex procedure that often justifies replacement of the entire locking device. Recall that, in a padlock, sliding the interchangeable core along its longitudinal axis allows the interchangeable core to slide out of the padlock housing for replacement. In a hockey puck lock, however, the locking operation requires the shackle (along with the attached central cylinder) to slide along its longitudinal axis into the cylindrical cavity before they lockingly engage. That is, if sliding along the longitudinal axis is utilized to remove the interchangeable core in a hockey puck lock, unlocking the lock may also cause the interchangeable core to be separated from the housing. Such frequent removal of the interchangeable core from the housing may be undesirable since the cores may be prone to loss or damage. Therefore, incorporating the interchangeable core concept of the padlock to the hockey puck lock, without causing the interchangeable core to be removed from the lock housing every time the lock is unlocked, is challenging.
U.S. Pat. No. 5,345,794 (the '794 patent) issued to Jenks on Sep. 13, 1994 describes a hockey puck lock (generally having structural details as described earlier) with a replaceable core. The replaceable core of the '794 patent is slidably retained within the lock housing by a locking pin. The protruding locking pin on an external surface of the replaceable core slides on an elongated slot on a mating surface of the housing, thereby retaining the replaceable core to the housing. To lock parallel plates with mating through holes using the lock of the '794 patent, the plates are positioned inside the rectangular cavity and the shackle attached to the replaceable core is slid through the mating through holes of the parallel plates and into the cylindrical cavity. While the replaceable core is in this locking position, an operator key causes the spring loaded locking pin to protrude into a pin recess located within the slot, thereby locking the shackle in position. To remove the replaceable core of the '794 patent from the housing, access holes are provided to manually depress the locking pin, by inserting a screw driver (or similar objects), while extracting the replaceable core from the housing.
While the hockey puck lock of the '794 patent enables replacement of the replaceable core when the operator key is lost, it may have some disadvantages. For example, the replaceable core of the '794 patent may be easily removed by an unauthorized person, thereby increasing the potential for loss, and increased replacement costs. In addition, in situations where the access holes can be accessed while the lock is in the locked position, the lock may be unlocked by depressing the locking pin through an access hole.
The present disclosure may overcome one or more of the shortcomings set forth above. The hockey puck lock of the current disclosure utilizes novel design features to retain the benefits of conventional hockey puck locks, while enabling the convenience of using commonly available interchangeable cores.